Destructive testing and failure analysis of a full-scale composite tidal turbine blade

Abstract

Tidal stream turbines play a pivotal role in harnessing marine energy, yet their reliability remains a critical challenge, impeding the cost-effectiveness of tidal energy. Deviations in blade performance can significantly impact turbine efficiency, potentially leading to unbalanced loads and consequential damage to the turbine and ad- jacent blades. Experience of blade failure, attributed to factors including material fatigue, manufacturing defects, environmental conditions, and operational stresses, under- scores the urgency for comprehensive investigation and development of mitigation strategies. This study addresses these challenges by subjecting a composite tidal blade to a series of incremental static and fatigue tests, culminating in controlled failure experiments conducted at the FastBlade structural fatigue testing facility. The facility’s advanced capabilities include a regenerative digital displacement hy- draulic pump system yielding substantial energy savings; an advanced multi-camera digital image correlation system; and an acoustic emission crack detection system. Using these we systematically explore the factors contributing to blade failure. The failure modes examined in this study include: metal-composite bond failure; crack propagation in thick-section composites; and adhesive failure of the hydrodynamic outer skin. Our findings have significant implications for the structural engineering, composite ma- terial, and tidal energy development communities. Notably, our study offers valuable insights into the mechanisms underlying both blade failure under extreme loads and the accumulation of damage in large, thick composite struc- tures. This research represents an important step towards enhancing the reliability and efficiency of tidal turbine blades, thus advancing the viability of tidal stream energy as a sustainable power source.